This invention relates to a duct type multizone air conditioning system for cooling and heating a plurality of air conditioning zones through ducts.
An air conditioning system for a residence has prevailed. Such an air conditioning system generally consists of cooling and heating air-to-air heat pump, an extremely cold time heating gas burner and a blower fan. One of the heat exchangers of the heat pump is installed out of door, and the other is disposed to be connected with the gas burner. This system has three operation modes as follows:
(1) A cooling operation mode which does not operate the gas burner but operates to cool the heat pump at a hot weather time,
(2) An ordinary heating operation mode which does not operate the gas burner at a cold weather time but operates to heat the heat pump, and
(3) An extremely cold weather heating operation mode which interrupts the heat pump at extremely cold time in which the efficiency of the heat pump is very low and operates to heat only with the gas burner as a heat source.
A space to be air conditioned in a residence at present is ordinarily divided into several rooms. Thus, a cooling and heating duct type air conditioning system in which a plurality of rooms of a space to be air conditioned (hereinbelow referred to as "zones") are cooled or heated through ducts by a central unit has widely been adopted.
However, only a thermostat for detecting room temperature is provided in the conventional duct type air conditioning system. Thus, there arise drawbacks that the respective zones to be air conditioned cannot be controlled individually at the temperatures, the zones cannot be maintained separately comfortably, and unnecessary energy is consumed to decrease the efficiency.